Mohawk–Hudson convergence (MHC) is a

mesoscale meteorology Mesoscale meteorology is the study of weather systems smaller than synoptic scale systems but larger than Microscale meteorology, microscale and storm-scale cumulus systems. Horizontal dimensions generally range from around 5 kilometers to several ...

phenomenon occurring over the

Capital District A capital district, capital region or capital territory is normally a specially designated administrative division where a country's seat of government is located. As such, in a federal model of government, no state or territory has any poli ...

region of

upstate New York Upstate New York is a geographic region consisting of the area of New York State that lies north and northwest of the New York City metropolitan area. Although the precise boundary is debated, Upstate New York excludes New York City and Long Is ...

, United States. The small

convergence zone A convergence zone in meteorology is a region in the atmosphere where two prevailing flows meet and interact, usually resulting in distinctive weather conditions. This causes a mass accumulation that eventually leads to a vertical movement a ...

forms within specific weather conditions sometimes found in the wake of

extratropical cyclone Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth. Extratropical cyclones are capable of ...

s shifting east of the area. Given

air pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The Standard atmosphere (unit), standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equival ...

decreasing with both longitude and latitude, as well as weak synoptic low-level flow, winds are channeled east along the

Mohawk Valley The Mohawk Valley region of the U.S. state of New York is the area surrounding the Mohawk River, sandwiched between the Adirondack Mountains and Catskill Mountains, northwest of the Capital District. As of the 2010 United States Census, th ...

and south through the

Hudson Valley The Hudson Valley (also known as the Hudson River Valley) comprises the valley of the Hudson River and its adjacent communities in the U.S. state of New York. The region stretches from the Capital District including Albany and Troy south to ...

, converging over Albany. With sufficient moisture in the lower atmosphere, a localized area of precipitation may form where the valleys meet, extending for several miles around Albany. The process manifests primarily in the lowest of the atmosphere. MHC-induced precipitation occurs predominately in the winter. It typically produces low clouds and light snowfall, often locally prolonging significant snow events by several hours. The strongest MHC events may yield snowfall rates approaching 1 in (2.5 cm) per hour. Occasionally, MHC contributes to shower and thunderstorm formation in the warm season. In early August 2008, two days of

training Training is teaching, or developing in oneself or others, any skills and knowledge or Physical fitness, fitness that relate to specific practicality, useful Competence (human resources), competencies. Training has specific goals of improving on ...

thunderstorms over the Capital District were attributed to MHC; the result was locally heavy rain, amounting to over . A relatively rare variation of MHC, termed "Southern Mohawk–Hudson convergence" (SMHC), occurs in the summer, when a southwesterly wind is present in advance of an approaching

cold front A cold front is the leading edge of a cooler mass of air at ground level that replaces a warmer mass of air and lies within a pronounced surface trough of low pressure. It often forms behind an extratropical cyclone (to the west in the Norther ...

. In that scenario, the Hudson and Mohawk valleys may direct the flow to become more southerly and westerly, respectively, yielding the formation of thunderstorms around Albany when conditions permit. As with MHC, SMHC is most pronounced in the absence of mechanisms for strong synoptic ascent over the region. Whereas the effects of the convergence zone are generally insignificant in the winter, SMHC presents more of a forecasting challenge when thunderstorms rapidly develop threaten and to impede travel at

Albany International Airport Albany International Airport is six miles (9 km) northwest of Albany, in Albany County, New York, United States. It is owned by the Albany County Airport Authority. ALB covers of land. It is an air port of entry in the town of Colon ...

. Thunderstorms associated with SMHC have the potential to become severe.

References

* * * * * Capital District (New York) Mesoscale meteorology {{climate-stub